When water is to be pumped out of an outdoor pit, reservoir, or canal, it is important to prevent debris, such as leaves, sticks, discarded plastic and paper articles, stones, etc., from entering the pump. Rotary self-cleaning strainers that contain cylindrical screens for performing the straining function are often used for this purpose.
The strainer is attached to the end of a conduit and placed in the body of water that is to be pumped. The pump is operated to suck water through the strainer and conduit, as the strainer screen prevents debris from being sucked into the conduit along with the water. Certain debris may adhere to the screen's exterior due to the pump suction force. However, the continued adherence of such debris to the screen's exterior, and resulting impairment of flow through the screen, are prevented by rotating the screen past a nozzle structure which is disposed on the interior of the screen and directs water outwardly through the screen to dislodge the debris. The water is fed under pressure to the strainer through a separate supply line which may be tapped into the pump's outlet. The water acts on only a limited circumferential zone of the screen at any given time to force adhering debris away from the exterior of the screen as the screen revolves past the nozzle structure. The remainder of the screen serves to pass the flow of water that is being sucked by the pump.
Commonly assigned U.S. Pat. Nos. 4,822,486; 5,108,592; 5,215,656; 5,356,532; 5,520,808 disclose new and improved rotary self-cleaning strainers of this general type. One feature of these strainers is the use of nozzles directed to eject pressurized water against the cylindrical screen to rotate the rotary portion of the strainer and simultaneously dislodge adhering debris from the exterior of the screen.
Annular end closure disks close the opposite axial ends of a rotary portion of the strainer to the non-rotating central core of the strainer. The core comprises a suction pipe through which water from the source being pumped is sucked out of the strainer, and a supply pipe that extends coaxially within the suction pipe to deliver pressurized water to the nozzles that are disposed at the radially outer ends of branch pipes which are threaded into the wall of the supply pipe. These end closure disks are rigid plastic. An axial end of the rotary portion may be closed to the suction pipe by either a single disk, or by a stack of plural disks. Mounted on these annular end closure disks are means providing for the journaling of the rotary portion on the non-rotating central core about the strainer's longitudinal axis.
In certain of these referenced patents the journaling of the upper end closure to the suction pipe is provided by a series of identical diameter wheels that are mounted on the lower face of the upper annular end closure to rotate about axes that are parallel with the strainer's longitudinal axis. For example, in one of the referenced patents there are four such wheels at ninety degree intervals around the axis of the strainer, defining an imaginary circle that is concentric with the strainer axis and slightly smaller than the inside diameter (I.D.) of the annular end closure such that the wheels just touch the outside diameter (O.D.) of the suction pipe. In two of the referenced patents, an annular seal is mounted on and sealed against the upper face of the upper end closure around the margin of its I.D. In radial cross section this seal has a lip that curves into sealing contact with the O.D. of the suction pipe. The lower end closure is journaled on the lower end of the central core, but the journaled surface of the central core is not the O.D. of the suction pipe.
One aspect of the present invention relates to a rotary self-cleaning strainer that can be fabricated with improved economy and that can exhibit improved operational performance. By utilizing all-wheel journaling, greater use is made of common parts, such as journal wheels and bushings, and special sealing arrangements, such as lip-type seals and stacks of sealing disks like those shown in certain of the referenced patents, can be eliminated. The disclosed all-wheel journaling is believed also to provide less frictional resistance, thereby making the inventive strainer more efficient to operate. Such improved efficiency offers the potential for effective usage with lower pressure pumps. Since pump pressures available at certain sites where the strainers are used are sometimes limited, the inventive strainer offers the opportunity for usage at such sites, thereby providing more widespread usage for such strainers.
PVC pipe is useful for both suction and supply pipes. In certain uses of strainers described in one or more of the above-referenced patents, it has been observed that the journal wheels on the upper end closure may eventually cause wear on the PVC suction pipe. A result is that the journaling becomes looser. It is believed that a strainer embodying principles of the present invention can reduce this type of wear and loosening by providing around the PVC suction pipe, a wear sleeve on which the upper end closure journal wheels ride.
Another aspect of the invention relates to elimination of the supply pipe end closure cap as a device for also securing the lower end closure and seal on the strainer. Therefore, a seal between the supply pipe and the lower end closure becomes unnecessary, and tightening of the supply pipe end closure cap is precluded from having any effect on the lower end closure.
Still another aspect of the invention relates to the construction of the frame that supports the strainer screen, including the end closures and tie rod structures that join the end closures in assembly. By utilizing several disks assembled together, an end closure may be fabricated by cutting each of the individual disks from flat sheet material. The tie rod structures can be accurately located and securely related to the end closures without the necessity of machining counterbores in the end closures. Structural strength can be increased by including one or more rings in association with the tie rod structures between the end closures.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which are accompanied by drawings. The drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at this time for carrying out the invention.